Nonreciprocal charge transport in quantum materials: From superconductors to magnetic systems.

Nonreciprocal charge transport, where current flows preferentially in one direction, has become a key topic across quantum materials. This review covers some recent progress in bulk crystals, artificial heterostructures, van der Waals systems, high-temperature superconductors, and magnetic materials. The review discusses both intrinsic origins, such as band-structure effects, and extrinsic ones, including vortex motion, device geometry, and heating artifacts. A central focus is the superconducting diode effect due to its application potential, which shows different critical currents for opposite directions. The review also examines how symmetry breaking, spin-orbit coupling, and magnetic order contribute to the observed responses. However, there remain challenges when many exciting findings lack a unified picture, and the field continues to debate the relative importance of various mechanisms. The review highlights key open questions and suggests future directions, including better experimental standards and device integration. This review aims to give a balanced view of what is known, what is uncertain, and where the field might go next.